1. Field
An embodiment of the present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device that has a lighting test circuit.
2. Description of Related Art
Recently, various flat panel displays that are lighter in weight and smaller in volume than that of a comparable cathode ray tube, have been developed. A flat panel display can be categorized as a liquid crystal display (LCD) device, a field emission display (FED) device, a plasma display panel (PDP), an organic light emitting display (OLED) device, etc.
An organic light emitting display (OLED) device is a flat panel display that displays an image using organic light emitting diodes that emit light by re-combining electrons and holes, and has a relatively rapid response speed and low power consumption so that it has been spotlighted as a next generation display.
Such an organic light emitting display device includes a pixel unit that includes a plurality of pixels, a scan driving circuit that supplies scan signals to the pixel unit, and a data driving circuit that supplies data signals to the pixel unit.
Here, the pixel unit and the scan driving circuit may be formed together on a panel by utilizing a low temperature poly-si (LTPS) process, and the data driving circuit may be mounted in the form of a driving IC chip on the panel after the LTPS process, etc. is completed.
However, a light test for confirming whether pixels can be normally (properly) lighted should be performed before the driving integrated circuit (IC) with the built-in data driving circuit is mounted. In order to perform such a lighting test, a separate lighting test circuit may be formed on the panel.
The lighting test circuit includes a plurality of switching devices that supply lighting test signals to data lines in accordance with test control signals supplied from the outside. Here, the switching devices may be composed of transistors that are formed during the LTPS process for forming transistors provided in a pixel circuit and a scan driving circuit, etc. In order to enhance manufacturing efficiency, the transistors of the switching devices have the same (or substantially the same) structure as the transistors of the pixel circuit and the scan driving circuit, etc.
However, the transistors provided in the lighting test circuit may be exposed to static electricity (ESD) flowed from the outside so that they may be damaged by static electricity during the LTPS process or even in the module state after the LTPS process is completed.
If the transistors of the lighting test circuit are damaged by static electricity, driving errors of the organic light emitting display device may result and/or the lighting test cannot be effectively performed.
Therefore, in an organic light emitting display device that performs a lighting test with a lighting test circuit before the driving IC is mounted, the lighting test circuit should be protected from damage caused by static electricity during the LTPS process or even in the module state after the LTPS process is completed.
To this end, there is a need to design the transistors of the lighting test circuit in a structure capable of protecting itself from static electricity.